text: I think the meaning of the とみる you are seeing is probably best rendered in English as "thought to" or "believed to". This isn't far from the "regarded" sense.
  
  For the sentence:
  
  
    現場の海域や付近の海岸では、これまでにも北朝鮮から来たと見られる木造船がたびたび見つかっていて、海上保安部は２人が北朝鮮から来たとみて、さらに詳しく調べています。
  
  
  現場の海域や付近の海岸では、 → In the sea and coast line near where this happened,
  これまでにも → until now
  北朝鮮から来たと見られる木造船 → wooden boats thought to have come from North Korea (at least in English Korea is at best ambiguous and at worst means South Korea)
  がたびたび見つかっていて → have been frequently seen
  海上保安部は → the coast guard
  ２人が北朝鮮から来たとみて → two people who are thought to come from North Korea
  さらに詳しく調べています。 → investigating more thoroughly
  
  
  海上保安部 = coast guard.
  
  Piecing it all back together:
  
  
    In the sea and along the coast near where the incident happened, until now wooden boats thought to be from North Korea have been frequently seen, and the coast guard is investigating more thoroughly the two men* who are thought to have come from North Korea.
  
  
  *at least in my dialect saying "men" here makes better sense than saying people.